TWI536431B - Method for permanent bonding of wafers - Google Patents

Description

Method of permanently bonding wafers

The present invention relates to a method for bonding a first contact surface of a first substrate to a second contact surface of a second substrate, as claimed in claim 1.

The goal of permanent or irreversible bonding of the substrate is to create an interconnection that is as strong as possible and, in particular, as irreversible as possible, thus creating a high bonding force between the two contact surfaces of the substrate. In the prior art, there are various ways and production methods for this purpose.

The known production methods and approaches followed so far often result in non-renewable or only poorly reproducible and in particular almost impossible to apply to modified conditions. In particular, the production methods currently used often use high temperatures (especially >400 ° C) in order to ensure reproducible results.

Due to the high temperatures that have hitherto been necessary for high bonding forces to some extent well above 300 ° C, various technical problems such as high energy consumption and possible damage to the structures present on the substrate are caused.

Other needs exist in the following areas:

- Front-end process compatibility.

This is defined as the compatibility of the process during the production of the electroactive component. The bonding process must therefore be designed such that the active components (such as transistors) already present on the structured wafer are neither adversely affected nor damaged during processing. The compatibility criteria mainly include the purity of certain chemical elements (mainly in CMOS structures) and are mainly affected by The mechanical load capacity affected by thermal stress.

- Low pollution.

- Do not apply force.

- The temperature is as low as possible, especially for materials with different coefficients of thermal expansion.

The reduction in bonding force results in a more careful handling of the structural wafer and thus a reduction in the probability of failure caused by direct mechanical loading.

The object of the invention is therefore to devise a method for producing a permanent joint with the highest possible joining force while carefully producing the lowest possible temperature.

This goal is achieved by the features of Technical Solution 1. Advantageous developments of the invention are given in the dependent technical solutions. All combinations of at least two of the specification, the scope of the claims, and/or the features set forth in the drawings also fall within the structure of the invention. Values within the indicated limits will also be considered as boundary values and will be claimed in any combination.

The basic idea of the present invention is to design a reservoir for holding a first eluent on at least one of the substrates, the eluent being present in the second substrate after contact or generation of temporary bonding between the substrates The eluent reacts and thus forms an irreversible or permanent bond between the substrates. Substantial cleaning of the or the substrates (especially by a rinsing step) is performed before or after the reservoir is formed in one of the reservoir forming layers on the first contact surface. This cleaning should generally ensure that there are no particles on the surface that would result in unjoined sites. The sedimenting agent contained in the reservoir and the reservoir generates at least one of the contact surfaces, in particular by reacting, after a temporary or reversible joining in a dedicated manner Preferably, the contact surface deformation opposite the reservoir induces a reaction that increases the joint speed and enhances the permanent joint directly on the contact surface (the first separating agent or the first group and the second separating agent or the second group) ) technical possibilities. As claimed in the present invention, on the opposite second contact surface, there is a growth layer in which deformation as claimed in the present invention and the first eductant (or first group) and the second substrate are present The second eductant (or the second group) present in the reaction layer is reacted. In order to accelerate the reaction between the first separating agent (or the first group) and the second separating agent (or the second group), as claimed in the present invention, the reaction layer and the reservoir positioned on the second substrate are specified The growth layer between the layers is thinned before the substrate is brought into contact, because in this way, the distance between the reaction partners is reduced and at the same time the deformation/formation of the growth layer as claimed in the present invention is promoted. The growth layer is preferably removed at least in part, especially in most, preferably completely. Even if the growth layer has been completely removed, the growth layer can be grown again in the reaction of the first separating agent and the second separating agent.

As claimed in the present invention, there may be used, especially by the passivation layer of the second substrate of the reaction, preferably by exposure to N ₂ before contact surface, forming gas, or an inert atmosphere or under a vacuum or by amorphous A member that inhibits the growth of the growth layer. In this connection, it has proven to be particularly suitable by the treatment of a plasma containing a forming gas, in particular mainly composed of a forming gas. Here, the gas is defined as a gas containing at least 2%, preferably 4%, ideally 10% or 15% hydrogen. The remainder of the mixture consists of an inert gas such as, for example, nitrogen or argon.

Alternatively or in addition to this measure, as claimed in the present invention, it is advantageous to minimize the time between thinning and contact, especially < 2 hours, preferably <30 minutes, even better <15 minutes, ideally <5 minutes. Therefore, oxide growth occurring after thinning can be minimized.

The rate of diffusion of the eluent through the growth layer is increased by the growth layer which has been thinned and thus extremely thin at least at the beginning of the formation of the permanent bond or at the beginning of the reaction. This results in a shorter delivery time of the eductant at the same temperature.

For the pre-bonding step, in order to create a temporary or reversible bond between the substrates, there are various possible ways of creating a weak interaction between the contact surfaces of the substrates. The pre-bonding strength is at least 1/2 to 1/3, especially 1/5, preferably 1/15, and more preferably 1/25 of the permanent joint strength. As a reference value, a pre-bonding strength having a pure non-activated hydrophilic hydrazine of about 100 mJ/m ² and a pure plasma-activated hydrophilic enthalpy of about 200 mJ/m ² to 300 mJ/m ² is mentioned. Pre-bonding between molecularly wetted substrates occurs primarily due to van der Waals interactions between molecules on different wafer sides. Thus, molecules having substantially permanent dipole moments are suitable for achieving pre-bonding between wafers. The following chemical compounds are mentioned as interconnecting agents, which are examples but are not limited thereto

-water

-thiol

-AP3000

- decane and / or

- stanol.

As claimed in the present invention, a substrate is a substrate whose material can react as an eductant with another supplied eluent to form a product having a higher molar volume, as a result of which a growth layer is formed on the substrate. the following Combinations are particularly advantageous, the isolating agent is specified on the left side of the arrow, and the product/products are designated on the right side of the arrow without the supply of the educting agent or by-product that reacts with the specifically designated eluent:

-Si→SiO ₂ , Si ₃ N ₄ , SiN _x O _y

-Ge→GeO ₂ , Ge ₃ N ₄

-α-Sn→SnO ₂

-B→B ₂ O ₃ , BN

-Se→SeO ₂

-Te→TeO ₂ , TeO ₃

-Mg→MgO, Mg ₃ N ₂

-Al→Al ₂ O ₃ , AlN

-Ti→TiO ₂ , TiN

-V→V ₂ O ₅

-Mn→MnO, MnO ₂ , Mn ₂ O ₃ , Mn ₂ O ₇ , Mn ₃ O ₄

-Fe→FeO, Fe ₂ O ₃ , Fe ₃ O ₄

-Co→CoO, Co ₃ O ₄ ,

-Ni→NiO, Ni ₂ O ₃

-Cu→CuO, Cu ₂ O, Cu ₃ N

-Zn→ZnO

-Cr→CrN, Cr ₂₃ C ₆ , Cr ₃ C, Cr ₇ C ₃ , Cr ₃ C ₂

-Mo→Mo ₃ C ₂

-Ti→TiC

-Nb→Nb ₄ C ₃

-Ta→Ta ₄ C ₃

-Zr→ZrC

-Hf→HfC

-V→V ₄ C ₃ , VC

-W→W ₂ C, WC

-Fe→Fe ₃ C, Fe ₇ C ₃ , Fe ₂ C

The following hybrid forms of semiconductors can also be thought of as substrates:

-III-V: GaP, GaAs, InP, InSb, InAs, GaSb, GaN, AlN, InN, Al _x Ga _Ix As, In _x Ga _Ix N

-IV-IV: SiC, SiGe,

-III-IV: InAlP,

- Nonlinear optics: LiNbO ₃ , LiTaO ₃ , KDP (KH ₂ PO ₄ )

- Solar cells: CdS, CdSe, CdTe, CuInSe ₂ , CuInGaSe ₂ , CuInS ₂ , CuInGaS ₂

- Conductive oxide: In _2-x SnxO _3-y

As claimed in the present invention, on at least one of the wafers, directly on the respective contact surfaces, there is a reservoir (or reservoirs) for a specific amount of the supplied segregation agent for the volume expansion reaction. At least one of them can be stored in a reservoir. The eluent may thus be, for example, O ₂ , O ₃ , H ₂ O, N ₂ , NH ₃ , H ₂ O ₂ or the like. Due to the expansion, especially governed by oxide growth, the possible gaps, voids, and cavities between the contact surfaces are minimized based on the tendency of the reaction partners to reduce system energy, and thus by virtue of the substrates in such regions The distance between the ends is narrowed and the joining force is increased. Under the best possible conditions, the existing gaps, voids and cavities are completely closed such that the entire joint area is increased and thus the joint force as claimed in the present invention rises accordingly.

The contact surface is conventionally shown to have a roughness of a secondary roughness (R _q ) of 0.2 nm. This corresponds to the peak-to-peak value of the surface in the range of 1 nm. These empirical values are determined by atomic force microscopy (AFM).

As claimed in the present invention, the reaction is suitable for allowing the growth layer to grow from 0.1 nm to 0.3 nm for a conventional wafer surface having a single water monolayer (ML) having a circular wafer having a diameter of 200 mm to 300 mm. .

As claimed in the invention, it is therefore provided in particular that at least 2 ML, preferably at least 5 ML, even more preferably at least 10 ML of the fluid, in particular water, is stored in the reservoir.

It is especially preferred to form the reservoir by exposure to the plasma, which is because the plasma exposure additionally results in smoothing and hydrophilicity of the contact surface as a synergistic effect. The surface system is smoothed by the activation of the plasma mainly by the viscous flow of the reservoir forming layer and optionally the material of the reaction layer. The increase in hydrophilicity is particularly due to the increase in the cerium hydroxide compound, preferably due to the cleavage of Si-O compounds (such as Si-O-Si) present on the surface, especially depending on the following reaction:

Another side effect (especially as a result of the above effects) is that the pre-bonding strength is particularly increased by a factor of two to three.

The reservoir system in the reservoir forming layer on the first contact surface of the first substrate (and optionally the reservoir forming layer on the second contact surface of the second substrate), for example, by already having a thermal oxide The plasma of the coated first substrate is activated to form. Plasma activation is performed in the vacuum chamber to enable adjustment of the conditions required for the plasma. As claimed in the present invention, for plasma discharge, N ₂ gas, O ₂ gas or argon having an ion energy in the range from 0 eV to 2000 eV is used, resulting in a treated surface (in this case, the first contact) The surface of the reservoir has a depth of up to 20 nm, preferably up to 15 nm, more preferably up to 10 nm, and optimally up to 5 nm. As claimed in the present invention, any particle type (atoms and/or molecules) suitable for use in generating a reservoir can be used. Preferably, the atoms and/or molecules that produce the reservoir having the desired properties are used. The relevant properties are mainly pore size, pore distribution and pore density. Alternatively, as claimed in the present invention, a gas mixture such as air or a forming gas composed of 95% Ar and 5% H ₂ may be used. Depending on the gas used, the following ions are especially present during the plasma treatment in the reservoir: N+, N ₂ +, O+, O ₂ +, Ar+. The first eductant can be contained in the unoccupied free space of the/these reservoirs. The reservoir forming layer and thus the reservoir can extend into the reaction layer.

Advantageously, there are different types of plasma materials which are reactive with the reaction layer and which are at least partially, preferably mostly composed of the first eductant. Concerning the second agent is isolated in terms of Si / Si, O _x species plasma would be advantageous.

The reservoir is formed based on the following considerations: a pore size of less than 10 nm, preferably less than 5 nm, more preferably less than 1 nm, even more preferably less than 0.5 nm, and most preferably less than 0.2 nm.

The pore density is preferably proportional to the density of the particles which generate the pores by impact, preferably even due to the partial pressure of the impact material, and depends on the processing time and in particular the parameters of the plasma system used.

Preferably, the pore distribution has at least one region of maximum pore density below the surface by superimposing to a plurality of such regions in the preferred plateau region (see Figure 7). The change in the parameters is achieved. The pore distribution converges to zero as the depth increases. The zone near the surface during bombardment has a pore density that is almost the same as the pore density near the surface. After the end of the plasma treatment, the pore density on the surface can be reduced as a result of the stress relaxation mechanism. The pore distribution in the thickness direction has a steep side with respect to the surface and a relatively flat but continuously decreasing side flap relative to the block (see Figure 7).

Similar considerations apply to all methods not produced by plasma for pore size, pore distribution and pore density.

The reservoir can be designed by controlled use and combination of process parameters. Figure 7 shows an indication of the concentration of nitrogen atoms injected by the plasma as a function of penetration depth into the ruthenium oxide layer. It is possible to generate two profiles by varying the physical parameters. The first section 11 is produced by faster accelerated atoms in the yttrium oxide, and conversely the profile 12 is produced at a lower density after changing the process parameters. The superposition of the two profiles produces a summation curve 13, which sums the characteristics of the reservoir. The relationship between the concentration of injected atoms and/or molecular species is significant. Higher concentrations indicate areas with higher defects and therefore have more space to accommodate subsequent segregation agents. The continuous change of process parameters, especially controlled in a dedicated manner during plasma activation, makes it possible to achieve a reservoir with increased ion distribution over depth, which is as uniform as possible.

As an alternative to a reservoir created by a plasma, it is contemplated to use a TEOS (tetraethyl orthosilicate) oxide layer on at least one of the substrates (at least the first substrate). This oxide is generally looser than the thermal oxide, and for this reason, compaction is advantageous, as claimed in the present invention. Compaction occurs by heat treatment with the goal of setting the specified porosity of the reservoir.

According to an embodiment of the invention, the filling reservoir may occur particularly advantageously with the formation of a reservoir by applying a reservoir as a coating to the first substrate, the coating already comprising a first separating agent.

The reservoir can be envisioned as a porous layer having a porosity in the nanometer range or a layer having a channel, wherein the channel density is less than 10 nm, more preferably less than 5 nm, even more preferably less than 2 nm, and most preferably less than 1 nm Especially best less than 0.5 nm.

For the step of filling the reservoir by the first group of the first separating agent or the separating agent, as claimed in the present invention, the following embodiments (also a combination) are conceivable: - exposing the reservoir to the ambient atmosphere, - By rinsing with especially deionized water, by rinsing with a fluid containing an eductor (especially H ₂ O, H ₂ O ₂ , NH ₄ OH) or by a separating agent, the reservoir is exposed to any gas atmosphere, In particular, atomic gas, molecular gas, gas mixture, - exposing the reservoir to an atmosphere containing water vapor or hydrogen peroxide vapor and - depositing a reservoir that has been filled with a separating agent as a reservoir forming layer On the substrate.

The following compounds may act as segregating agents: O _x ⁺ , O ₂ , O ₃ , N ₂ , NH ₃ , H ₂ O, H ₂ O ₂ and/or NH ₄ OH.

The use of the above hydrogen peroxide vapor is considered to be a preferred version in addition to the use of water. Furthermore, hydrogen peroxide has the advantage of having a large ratio of oxygen to hydrogen. In addition, hydrogen peroxide dissociates into hydrogen and oxygen at certain temperatures above and/or via the use of high frequency fields in the MHz range.

It is advantageous to use a method for dissociating the above substances, mainly when using materials having different coefficients of thermal expansion, without using any notable temperature increase or at best causing local/specific temperature increase. In particular, there is at least microwave radiation that promotes, preferably results in, dissociation.

According to an advantageous embodiment of the invention, the formation of the growth layer and the strengthening of the irreversible bonding are defined by diffusion of the first separating agent into the reaction layer.

According to a further advantageous embodiment of the invention, the formation of the irreversible joint is preferably at a temperature which is generally less than 300 ° C, advantageously less than 200 ° C, more preferably less than 150 ° C, even more preferably less than 100 ° C, optimal. Occurs at room temperature, especially at most 12 days, more preferably up to 1 day, even more preferably up to 1 hour, optimally up to 15 minutes. Another advantageous heat treatment method is dielectric heating by microwave.

Here, it is particularly advantageous if the irreversible joint has a joint strength of more than 1.5 J/m ² , especially more than 2 J/m ² , preferably more than 2.5 J/m ² .

The bonding strength can be particularly advantageously increased because during the reaction, as claimed in the present invention, a product having a molar volume larger than the molar volume of the second separating agent is formed in the reaction layer. In this way, growth on the second substrate is achieved, as a result of which the gap between the contact surfaces can be closed by a chemical reaction, as claimed in the present invention. As a result, the distance between the contact surfaces (and thus the average distance) is reduced, and the dead space is minimized.

In the case of reservoir formation by plasma activation, especially at an activation frequency between 10 kHz and 600 kHz and/or a power density between 0.075 watt/cm ² and 0.2 watt/cm ² and/or a pressure of 0.1 In the case of a pressurization between mbar and 0.6 mbar, an additional effect such as smoothing of the contact surface and a significant increase in the hydrophilicity of the contact surface is achieved.

As an alternative thereto, as claimed in the present invention, a reservoir can be formed by using a tetraethoxydecane oxide layer compacted to a certain porosity in a controlled manner as a reservoir forming layer.

According to a further advantageous embodiment of the invention, it is provided that the reservoir-forming layer consists essentially, in particular essentially exclusively, of amorphous amorphous cerium oxide, in particular amorphous cerium oxide produced by thermal oxidation, and the reaction layer consists of The oxidizable material, in particular predominantly, preferably consists essentially entirely of Si, Ge, InP, GaP or GaN (or another material as mentioned above alternatively). Particularly stable reactions that effectively close existing gaps are achieved by oxidation.

Here, as claimed in the present invention, it is provided that between the second contact surface and the reaction layer there is a growth layer which is predominantly predominantly of primary cerium oxide (or another material mentioned above alternatively). As claimed in the present invention, the growth layer is subjected to growth caused by the reaction. Especially in the region with the reaction layer, and in particular in the region of the gap between the first contact surface and the second contact surface, by the re-formation of the amorphous SiO ₂ and the resulting deformation of the growth layer (especially convex The growth is produced by the conversion of Si-SiO ₂ (7). This results in a decrease in the distance between the two contact surfaces or a decrease in the dead space, as a result of which the joint strength between the two substrates increases. A temperature between 200 ° C and 400 ° C, preferably between about 200 ° C and 150 ° C, more preferably between 150 ° C and 100 ° C, and preferably between 100 ° C and room temperature is particularly advantageous. The growth layer can be divided into several growth zones. The growth layer can simultaneously form a reservoir for the reservoir of the second substrate in which another reservoir that accelerates the reaction is formed.

Here, if the growth layer is formed at 0.1 nm before irreversible bonding is formed An average thickness A between 5 nm is particularly advantageous. The thinner the growth layer, the faster and easier the reaction between the first eluent and the second eluent via the growth layer, especially by diffusion of the first eluent through the growth layer to the reaction layer. The rate of diffusion of the eluent through the growth layer is increased by the growth layer which has been thinned and thus extremely thin at least at the beginning of the formation of the permanent bond or at the beginning of the reaction. This results in less delivery time of the eluent at the same temperature.

Here, as claimed in the present invention, thinning can play a decisive role because the reaction can be further accelerated and/or the temperature can be further reduced. The thinning can be carried out, in particular, by etching, preferably in a humid atmosphere, and more preferably in situ. Alternatively, the thinning preferably occurs in situ, especially by dry etching. Here, in situ means performing in the same chamber in which at least one previous step and/or a subsequent step is performed. Another system included in the concept of in situ used herein is configured as a system in which the transport of substrates between individual process chambers can be adjusted in a controlled manner (eg, using an inert gas) But especially in a vacuum environment. Wet etching occurs by chemicals in the vapor phase, while dry etching occurs by chemicals in a liquid state. In the case where the growth layer is composed of cerium oxide, etching by hydrofluoric acid or diluted hydrofluoric acid can be performed. In the case where the growth layer is composed of pure Si, etching can be performed by KOH.

According to an embodiment of the invention, it is advantageously provided that the formation of the reservoir is performed in a vacuum. Therefore, contamination of the reservoir by unwanted materials or compounds can be avoided.

In another embodiment of the invention, it is advantageously provided that the filling of the reservoir occurs by one or more of the following steps: - exposing the first contact surface to the atmosphere for use in the air Containing atmospheric humidity and/or oxygen-filled reservoirs - exposing the first contact surface to a fluid which is especially predominantly (preferably almost completely) consisting of, in particular, deionized H ₂ O and/or H ₂ O ₂ - The first contact surface is exposed to N ₂ gas and/or O ₂ gas and/or Ar gas, in particular having an ion energy in the range from 0 eV to 2000 eV and/or especially from 95% of Ar and 5% of H ₂ constituent gas formation, vapor deposition for filling the reservoir by any of the specified eductants.

If the reservoir is preferably between 0.1 nm and 25 nm, more preferably between 0.1 nm and 15 nm, even more preferably between 0.1 nm and 10 nm, optimally between 0.1 nm and 5 nm The formation of the thickness R is particularly effective for the program sequence. Furthermore, according to an embodiment of the invention, the average distance B between the reservoir and the reaction layer immediately before the formation of the irreversible bond is between 0.1 nm and 15 nm, in particular between 0.5 nm and 5 nm, It is preferably between 0.5 nm and 3 nm. As claimed in the present invention, the distance B is affected or produced by thinning.

As claimed in the present invention, a device for performing a method is provided, the device having: a chamber for forming a reservoir; a chamber that is provided, in particular, separately for filling the reservoir; A chamber, provided separately, for forming a pre-engagement, all chambers being directly connected to each other via a vacuum system.

In another embodiment, the filling of the reservoir can also occur directly through the atmosphere, so that the wafer can be disposed of semi-automatically and/or completely automatically in a chamber that is open to the atmosphere or simply without a seal. Structurally occurring.

Other advantages, features, and details of the present invention will become apparent from the following description of the preferred embodiments.

In the figures, the same or equivalent features are identified by the same reference numerals.

The chemical reaction shown in Figure 1 and during the pre-bonding step between the first contact surface 3 of the first substrate 1 and the second contact surface 4 of the second substrate 2 or immediately after the pre-bonding step An extract is shown in the case [sic]. The surface is capped with a polar OH group and is therefore hydrophilic. The first substrate 1 and the second substrate 2 are held by the gravitational force of a hydrogen bridge between the OH group and the H ₂ O molecule present on the surface and also between the H ₂ O molecules alone. At least the hydrophilicity of the first substrate 1 has been increased by the plasma treatment in the previous step.

According to an alternative embodiment, it is especially advantageous to additionally subject the second substrate 2 or the second contact surface 4 to a plasma treatment, simultaneously with the plasma treatment of the first substrate 1.

As claimed in the present invention, the reservoir 5 in the reservoir forming layer 6 composed of hot cerium oxide has been formed by plasma treatment and in the reservoir forming layer 6 in an alternative embodiment according to Fig. 1b. 'The second relative reservoir 5'. Below the reservoir forming layers 6, 6', the second layer of reaction layers 7, 7' containing the second separating agent or separating agent are directly adjacent. Plasma treatment of O ₂ ions in the range of ion energy between 0 eV and 2000 eV produces an average thickness R of the reservoir 5 of approximately 15 nm, which forms channels or pores in the reservoir forming layer 6 .

Between the reservoir forming layer 6 and the reaction layer 7, there is a growth layer 8 on the second substrate 2, which may be at least partially a reservoir forming layer 6' at the same time. Therefore, another growth layer may additionally exist between the reservoir forming layer 6' and the reaction layer 7'.

Similarly, prior to the step shown in FIG. 1 and after the plasma treatment at least predominantly as a segregation reducing agent of the first H ₂ O filled reservoir 5 (and optionally the reservoir 5 '). The reduced ionic species present in the plasma process can also be located in the reservoir, especially O ₂ , N ₂ , H ₂ , Ar.

Before or after the formation of the/the reservoirs 5, 5', the growth layer 8 (and optionally other growth layers) is thinned by etching under any conditions before the substrates 1, 2 are contacted (here After forming the reservoir 5, see Figure 2). In this way, the average distance B between the second contact surface 4 and the reaction layer 7 is reduced. At the same time, the second contact surface 4 is advantageously relatively flat.

After the contacting in the stages shown in Figures 1a and 1b, the contact surfaces 3, 4 still have a relatively wide gap, which is governed in particular by the water present between the contact surfaces 3, 4. Therefore, the existing joint strength is relatively low and is approximately between 100 mJ/cm ² and 300 mJ/cm ² , especially more than 200 mJ/cm ² . In this connection, previous plasma activation plays a decisive role, especially due to the increased hydrophilicity of the first contact surface 3 activated by the plasma and the smoothing effect caused by plasma activation.

The process shown in Figure 1 and referred to as pre-bonding can preferably be carried out at ambient temperature or at a maximum of 50 degrees Celsius. Figures 3a and 3b show a hydrophilic bond that occurs as the Si-O-Si bridge splits the water by the -OH capping surface. Figure 3a and Figure 3b The process in the process lasts for approximately 300 h at room temperature. About 60 h at 50 °C. The state in Figure 3b occurs at the indicated temperature without generating reservoir 5 (or reservoir 5, 5').

Between the contact surfaces 3, 4, H ₂ O molecules are formed, and the H ₂ O molecules are at least partially used to further fill the reservoir 5 to a range where free space still exists. Other H ₂ O molecules were removed. In the step according to Figure 1, there are approximately 3 to 5 individual OH groups or H ₂ O layers, and from the step according to Figure 1 to the step according to Figure 3a, 1 to 3 H ₂ O monolayers are removed or It is housed in the reservoir 5.

In the step shown in Fig. 3a, a hydrogen bridge is now formed directly between the oxiranyl groups, as a result of which a large bonding force occurs. This more strongly pulls the contact surfaces 3, 4 to each other and reduces the distance between the contact surfaces 3, 4. Therefore, there are only 1 to 2 individual OH base layers between the contact surfaces 1, 2.

In the step shown in Figure 3b, in addition to separating the H ₂ O molecules according to the reaction inserted below, a covalent compound in the form of a stanol group is now formed between the contact surfaces 3, 4, which results in a much stronger The joining force and requiring less space is such that the distance between the contact surfaces 3, 4 is further reduced until the contact surfaces 3, 4 are directly in contact with each other to finally reach the minimum distance shown in Figure 3:

Until stage 3, in particular due to the formation of the reservoir 5 (and optionally the additional reservoir 5'), it is not necessary to increase the temperature unduly, as it is, allowing it to be carried out even at room temperature. In this way, it is possible to carry out the process steps according to FIG. 1a or FIG. 1b to FIG. 4 with particular caution.

In the method steps shown in Figure 5, the temperature is preferably increased to a maximum of 500 ° C, more preferably up to 300 ° C, even more preferably up to 200 ° C, optimally up to 100 ° C, especially preferably not exceeding room temperature To form an irreversible or permanent bond between the first contact surface and the second contact surface. The only reason why these relatively low temperatures are possible compared to the prior art is that the reservoir 5 (and optionally the reservoir 5') contains the first segregation agent for the reactions shown in Figures 6 and 7. :Si+2H ₂ O → SiO ₂ +2H ₂

By increasing the H ₂ O molecule, especially at the interface between the reservoir forming layer 6 ′ and the reaction layer 7 (and optionally also at the interface between the reservoir forming layer 6 and the reaction layer 7 ′) Mohr volume and diffusion, due to the goal of minimizing the free Gibbs 焓 enhanced growth occurring in the zone in which the gap 9 exists between the contact surfaces 3, 4, in the growth layer 8 The volume of the form increases. The gap 9 is closed by an increase in the volume of the growth layer 8. More specifically: at the above slightly increased temperature, the H ₂ O molecule diffuses as a first segregant from the reservoir 5 (or the reservoir 5, 5') to the reaction layer 7 (and optionally 7'). This diffusion may be via direct contact of the reservoir forming layers 6, 6' formed as an oxide layer with the respective reaction layers 7, 7' (or growth layer 8) or via a gap 9 present between the oxide layers or Occurs from the gap 9. Here, cerium oxide (hence, a chemical compound having a larger molar volume than pure cerium) is formed as the reaction product 10 of the above reaction from the reaction layer 7. Cerium oxide is grown at the interface of the reaction layer 7 with the growth layer 8 and/or the reservoir formation layers 6, 6', and thus forms a growth layer 8, which is made in particular in the direction of the gap 9 as a native oxide. to make. H ₂ O molecules from the reservoir are also needed here.

Due to the presence of the gap in the nanometer range, there is a possibility that the growth layer 8 is convex, and as a result, the stress on the contact surfaces 3, 4 can be reduced. In this way, the distance between the contact surfaces 3, 4 is reduced, as a result of which the contact surface and thus the joint strength are further increased. In contrast to the partially unfused prior art products, the fusion joints that are closed in this manner and formed over the entire wafer are fundamentally contributing to increased bonding forces. The type of bonding between the two amorphous yttria surfaces fused to each other is a mixed form of covalent and ionic moieties.

The above reaction of the first separating agent (H ₂ O) with the second separating agent (Si) takes place in the reaction layer 7 particularly rapidly or at as low a temperature as possible, between the first contact surface 3 and the reaction layer 7 The average distance B is as small as possible.

Therefore, the pretreatment of the first substrate 1 and the selection/pretreatment of the second substrate 2 are decisive, and the second substrate 2 is composed of the reaction layer 7 of tantalum and the as thin as possible native oxide layer of the growth layer 8. There is a thin layer of native oxide that is as thin as possible for two reasons. The growth layer 8 is extremely thin (especially due to the thinning provided, as claimed in the present invention) such that the growth layer 8 can be oriented toward the opposite substrate 1 due to the newly formed reaction product 10 on the reaction layer 7. The reservoir forming layer 6 is convex, and the reservoir forming layer is formed into an oxide layer mainly in the region of the nano gap 9. Furthermore, a diffusion path that is as short as possible is required in order to achieve the desired effect as quickly as possible and at the lowest possible temperature. The first substrate 1 is also composed of a tantalum layer and an oxide layer formed thereon as a reservoir forming layer 6, and the reservoir 5 is at least partially or completely formed in the reservoir forming layer 6.

As claimed in the present invention, the reservoir 5 (or the reservoir 5, 5') is at least closed The amount of the first separating agent necessary for the nanogap 9 is filled so that the optimum growth of the growth layer 8 can occur in the shortest possible time and/or at the lowest possible temperature to close the nanogap 9 .

1‧‧‧First substrate

2‧‧‧second substrate

3‧‧‧First contact surface

4‧‧‧Second contact surface

5‧‧‧Reservoir

5'‧‧‧Reservoir

6‧‧‧ Reservoir formation layer

6'‧‧‧ Reservoir formation layer

7‧‧‧Reaction layer

7'‧‧‧Reaction layer

8‧‧‧ growth layer

9‧‧Non gap

10‧‧‧Reaction products

11‧‧‧ first section

12‧‧‧Second section

13‧‧‧sum curve

A‧‧‧average thickness

B‧‧‧average thickness

R‧‧‧average thickness

Figure 1a shows a first step of the method as claimed in the present invention immediately after the first substrate is in contact with the second substrate, and Figure 1b shows the claim as claimed in the present invention immediately after the first substrate is in contact with the second substrate. An alternative to the first step of the method, Figure 2 shows the steps occurring prior to the contacting of the process as claimed in the present invention, in particular the thinning of the second substrate, and Figures 3a and 3b show the method as claimed in the present invention. Other steps for forming a higher bond strength, FIG. 4 shows another step of the method as claimed in the present invention after the steps according to FIGS. 1a or 1b, 2 and 3a and 3b, wherein the substrate contact surface In contact, Figure 5 shows the steps for forming an irreversible/permanent bond between substrates as claimed in the present invention, and Figure 6 shows the chemical/physical on two contact surfaces during the steps according to Figures 4 and 5. Amplification of the process, Figure 7 shows another enlargement of the chemical/physical process performed at the interface between the two contact surfaces during the steps according to Figures 4 and 5, and Figure 8 shows the reservoir as claimed in the present invention The resulting graph of the device.

1‧‧‧First substrate

2‧‧‧second substrate

6‧‧‧ Reservoir formation layer

7‧‧‧Reaction layer

7'‧‧‧Reaction layer

8‧‧‧ growth layer

Claims (21)

A method of bonding a first contact surface (3) of a first substrate (1) to a second contact surface (4) of a second substrate (2) by the following steps, the second substrate (2) having at least one reaction a layer (7) comprising a second separating agent or a second group of the separating agent: forming a reservoir in the reservoir forming layer (6) on the first contact surface (3) (5) at least partially filling the reservoir (5) with a first group of the first separating agent or the separating agent, thinning the second substrate (2), after thinning the second substrate (2), Contacting the first contact surface (3) with the second contact surface (4) to form a pre-joined connection, and forming a permanent bond between the first contact surface and the second contact surface (3, 4), Permanently joining at least a portion of the first eluent or the first group of the eluent to the second eluent or the second eductor contained in the reaction layer (7) of the second substrate (2) The reaction of the group is strengthened. The method of claim 1, wherein the step of thinning the second substrate (2) is performed by etching. The method of claim 2, wherein the step of thinning the second substrate (2) comprises etching in a humid atmosphere. The method of claim 1, wherein the step of thinning the second substrate (2) is performed by dry etching. The method of any one of claims 1 to 4, wherein the method further comprises a reservoir formation on the second contact surface (4) of the second substrate (2) An additional reservoir (5') is formed in layer (6'). The method of claim 5, wherein the reservoir forming layer (6') on the second contact surface (4) is formed by plasma activation. The method of claim 5, wherein the additional reservoir (5') in the reservoir forming layer (6') on the second contact surface (4) is by using compacted tetraethoxy decane An oxide layer is formed as the reservoir forming layer (6'). The method of any one of claims 1 to 4, wherein during the reaction, a reaction product (10) having a molar volume larger than a molar volume of the second eductant is formed in the reaction layer (7). . The method of any one of claims 1 to 4, wherein the/the reservoirs (5, 5') are formed by plasma activation. The method of any one of claims 1 to 4, wherein the reservoirs (5, 5') are formed by using a compacted tetraethoxydecane oxide layer as the reservoir layer (6) ) formed. The method of any one of claims 1 to 4, wherein the reservoir forming layer (6) is composed of an amorphous material, and the reactive layer (7) is composed of an oxidizable material. The method of claim 1, wherein a growth layer (8) is present between the second contact surface (4) and the reaction layer (7), and the growth layer (8) is partially or completely moved by the thinning except. The method of claim 12, wherein the growth layer (8) is native cerium oxide. The method of claim 12 or 13, wherein the growth layer (8) has an average thickness A between 1 angstrom and 10 nm before the forming of the permanent joint and after the thinning. The method of any one of claims 1 to 4, wherein the forming of the reservoir is performed in a vacuum. The method of any one of claims 1 to 4, wherein the reservoir is filled by one or more of the steps described below: exposing the first contact surface (3) to having high oxygen and/or water a first atmosphere of the content, exposing the first contact surface (3) to a fluid consisting of deionized H ₂ O and/or H ₂ O ₂ , exposing the first contact surface (3) to N ₂ gas and/or O ₂ gas and / or Ar gas and / or a forming gas composed of 95% Ar and 5% H ₂ . The method of any one of claims 1 to 4, wherein the reservoir (5) is formed with an average thickness (R) between 0.1 nm and 25 nm. The method of any one of claims 1 to 4, wherein the average distance (B) between the reservoir (5) and the reaction layer (7) is at 0.1 nm immediately before the permanent bond is formed. Between 15nm. The method of claim 18, wherein the average distance (B) is between 0.5 nm and 5 nm. The method of claim 19, wherein the average distance (B) is between 0.5 nm and 3 nm. The method of any one of claims 1 to 4, wherein the permanent joint has a joint strength comprising twice the pre-bonding strength.